This invention relates to electric charging devices for batteries and, more particularly, to an electric coupling apparatus suited for electromagnetic type induction charging devices for use in self-propelled objects such as electric vehicles powered by batteries.
Non-contact type battery charging devices have heretofore been proposed to charge batteries of electric vehicles by means of electromagnetic, inductive charging.
Each of the battery charging devices includes a power supply charging device, which is located at a charging station and has a power supply coupler, and a power receiver charging device, which includes a power receiver coupler that is mounted, for example, in the vehicle. The power supply charging device and the power receiver charging device are electrically coupled to each other by coupling a power supply coupler 50 to a power receiver coupler 51 as shown in FIG. 7.
The power supply coupler 50 includes a paddle-shaped casing 50a. The casing 50a houses a primary core 52 and a primary coil 53. The power receiver coupler 51 includes a box-shaped casing 51a having an opening 56 into which the power supply coupler 50 is inserted. The casing 51a houses a secondary core 54 and a secondary coil 55.
When the power supply coupler 50 is inserted into the power receiver coupler 51, a closed magnetic flux circuit is formed between the cores 52 and 54. When an alternating electric current is supplied to the coil 53 from the power supply charging device, an electromotive force is induced in the secondary coil 55 of the power receiver charging device due to electromagnetic induction. This electric power is converted to direct electric power and is used to charge the battery of the vehicle.
In the above-mentioned prior art power receiver coupler, an extremely small gap is formed between a core member 60 and the power supply coupler 50, thereby providing a high charging rate. FIG. 8 shows a typical arrangement of cores of the power supply coupler and the power receiver coupler.
The primary core 52 of the power supply coupler 50 is located in the lower end of the casing 50a. Both ends of the primary core 52 are exposed. The coil 53 is assembled in the casing 50a, while wound around the primary core 52. The secondary core 54 of the power receiver coupler 51 includes a core member 59 and a core member 60. The core member 59 has a magnetic pole 57 and a pair of yokes 58, which extend upright at the ends of the magnetic pole 57. The core member 60 has a plate like configuration and is combined with the core member 59 to magnetically connect the yokes 58 to one another. A hollow is formed between the core members 59 and 60. The casing 50a of the power supply coupler 50 fits in the hollow. A secondary coil 55 is formed in a printed circuit board and has a bore formed in its center. The magnetic pole 57 fits in the bore and extends into the hollow between the cores 59 and 60.
In the prior art electric coupling devices discussed above, there is a great deal of heat generated by the coils 53 and 55 and the temperature of the cores 52 and 54 increases. The core 54 and the coil 55 in the power receiver coupler 51 are cooled by air that flows through the casing 5la. The core 52 and the coil 53 of the power supply coupler is cooled by the air surrounding the casing 50a.
In the structure mentioned above, the gap between the casing 50a and the core member 60 is extremely small and cooling air scarcely circulates through the gap. For this reason, the casing of the power receiver coupler 51 tends to overheat. The temperature of the coil 53, the core 52 and the core member 60 of the power receiver coupler 51 increase to an extremely high level.
When the temperature increases, the printed circuit board and other electric components may be damaged or malfunction.